探討大蒜素透過調節腸道菌以達到延緩動脈粥狀硬化之研究

Abstract

根據衛生福利部106年十大死因統計指出心臟疾病死因位居第二，僅次於癌症，綜觀前十大死因和心血管相關的疾病總死亡人數與癌症不相上下。此外，世界衛生組織 (World Health Organization, WHO) 早在2015年即公告CVD (cardiovascular disease) 為全球死因第一位，可見預防心血管疾病之重要性。心血管疾病的發生多與動脈粥狀硬化有關，其為一種慢性疾病，是血管內皮脂肪沉積形成斑塊進而造成血管失去彈性、管腔阻塞甚至引發血栓導致心肌梗塞、腦中風等急症發生。然而致病的進程是可以預防的，其中飲食因子與其息息相關。近年來研究發現，紅肉、蛋類等富含choline和carnitine之飲食來源，會透過腸道菌轉換生成TMA (Trimethylamine)，再經宿主肝臟酵素FMO3 (Flavin-containing monooxygenases) 代謝生成TMAO (Trimethylamine N-oxide) 進而促進動脈粥狀硬化 (Atherosclerosis) 形成。大蒜於中醫典籍當中記載其有解滯氣、暖脾胃、解毒殺蟲等作用，在許多研究亦證實具有殺菌、抗氧化、降低膽固醇等功能，其中大蒜素 (Allicin) 為其重要生物活性分子亦是香味來源。本研究欲透過大蒜素來抑制需經腸道菌作用生成TMAO的路徑，觀察長期以carnitine誘導促進ApoE(-/-) 小鼠斑塊生成模式下，大蒜素延緩動脈粥狀硬化之功效。實驗分組如下：(1) 控制組 (2) 1.3% 肉鹼組 (3) 大蒜素組 (10 mg/kg BW) (4) 1.3% 肉鹼搭配大蒜素組。結果顯示相較於單純給予carnitine組，在搭配大蒜素處理下主動脈斑塊生成減少。於短期試驗發現大蒜素搭配carnitine組別與carnitine組相比，血中TMAO濃度明顯下降。另外，利用主坐標分析 (Principal coordinates analysis, PCoA) 作圖觀察各組之間糞便菌相分佈具有顯著差異。由本實驗結果進一步了解大蒜素於調節腸道菌代謝生成TMAO以延緩動脈粥狀硬化之效用，更進一步說明了心¬-腸軸線之關聯性。

Red meat consumption can promote atherosclerosis since the gut microbiota can metabolize L-carnitine from meat into trimethylamine N-oxide (TMAO) which is a causative risk for cardiovascular disease. Garlic has long been associated with health benefits. Allicin is a major bioactive compound typically found in blend fresh garlic. It possesses the antibacterial, anti-oxidant, and cholesterol-lowering effects. The aim of this study is to investigate the effect allicin on the gut microbiota and its metabolites on cardiovascular disease by using the long-term carnitine treatment ApoE(-/-) mice model. 8-week old male ApoE(-/-) mice were divided into 4 groups: (1) Control, (2) 1.3% Carnitine, (3) Allicin (10mg/kg BW), and (4) 1.3% Carnitine + Allicin (10 mg/kg BW). After 15 weeks, we performed the carnitine challenge test by oral gavage of D9-carnitine to evaluate the TMAO production ability of the gut microbiota. The serum was analyzed for carnitine, trimethylamine (TMA) and TMAO levels by using LC-MS/MS. Morphological changes of aortic plaque formation were observed using oil red staining. The gut microbiome was analyzed by using 16S rDNA amplicon sequencing in Illumina Miseq platform. The results showed that allicin supplementation in the carnitine group exhibited the reduction of aortic lesion up to 34.2% as compared with carnitine group without allicin supplementation (p < 0.0001). The carnitine challenge test indicated the D9-TMAO level of carnitine with allicin supplementation group tend to be reduced compared with carnitine-fed mice. Principal coordinate analysis of the feces microbiota composition was significantly different (ADONIS: P < 0.001) for each group. Notably, in 2-week short-term animal study, we found that allicin could significantly reduce TMAO level on carnitine diet; the effect is superior than that of 15-week treatment. Allicin may exhibit the cardiovascular disease protective effect through modulation of gut microbiota-TMAO-atherosclerosis pathway.